A typical such light has a housing made of sheet steel that forms locking members directed inward in the housing for a bayonet-type mount or a screw attachment of a lens fitting over a light bulb or source, and that holds a socket for the light source. The lens has an approximately cup-like dome and a collar defining an opening and fittable into the housing. The collar is has L-shaped angularly distributed grooves formed by axially extending insertion groove legs for the locking members, and angularly extending holding groove legs adjacent thereto by means of which the lens may be fixed in an end position in the housing by performing an inserting-rotating motion. Each angularly extending groove leg has an outer flank on the opening side and by an inner flank on the dome side.
Such electrical lights are well known from the prior art, in particular as oven lights. The housing, which carries electrical connections for the light-bulb socket, is typically positioned and attached in a recess in the wall of an oven. The lens together with its threaded collar is inserted into this typically cup-like seat and is either screwed in or fixed in place in the manner of a bayonet lock, so that the light source in the housing, the connection elements, and the socket for the light source are protected from grease splatters or the like.
For cost reasons it has become customary to manufacture the housing from a stainless steel or surface-treated steel sheet that generally has stamped formations directed toward the interior of the housing that are used as locking sections or threaded sections for securing the lens to the housings, and that are referred to below as locking members. The lens usually has a stop surface, and is screwed into the housing until this stop surface is securely seated on a flanged edge of the housing.
Lenses having a groove on their collar for a bayonet-type mount also typically have a thread-like section in a region of the groove, so that here as well the stop surface may be axially tightened against the flanged edge of the housing by rotation.
To prevent the lens from becoming unscrewed, the threads of the lens have a very shallow pitch so that a certain self-locking of the thread is achieved. The lens is furthermore protected from becoming unscrewed as the result of its tightening torque, as well as the frictional adhesion thus produced between the flanged edge of the housing and the outer flank. A corresponding screw-in oven light is disclosed, for example, in U.S. Pat. No. 4,326,243 and German patent publication 2,921,425.
A common problem with the above-referenced oven lights is that, due to the high temperatures of 300° C., or up to 450° C. for self-cleaning ovens, the stop surface of the lens on the flanged edge of the housing and on the locking or threaded sections may bake on, so that the glass lens may no longer be unscrewed. This effect is intensified, particularly in the region of the flanged edge, by contamination during use of the appliance. In practice, when a defect is present in the light source in the oven light it is often necessary to destroy the lens in order to replace the bulb.
Furthermore, it has been found that not only is removal of the lens for maintenance made more difficult by the lens baking onto the flanged edge of the housing, an additional problem is the tightening torque of the lens that results in a certain stress on the housing, in particular in the region of the locking members. This further promotes the baking of the lens onto the housing. In addition, the inherently circular housing is deformed into a polygon as the result of screwing in the cover, which likewise interferes with the unscrewing motion for the lens.
Proceeding from this problem, DE 195 04 405 discloses an oven light having a small distance between the stop surface and the flanged surface of the housing. For this basically advantageous oven light, however, vapors may penetrate this gap and the installation opening for the oven light provided in the oven chamber, entering the cavity between the chamber and the outer oven wall. Over time, contamination results that may cause operational problems, since it is here that the essential control elements for the oven are located.